Method of manufacturing recombinant lectin protein and recombinant lectin protein manufactured by using the same

ABSTRACT

Provided is a recombinant BPL3 protein having β-GlcNAc-Sp and a glycan binding specificity, the recombinant BPL3 protein produced by synthesizing a recombinant BPL3 (rBPL3) gene encoding a Bryopsis plumosa lectin (BPL3) protein; preparing a tandem repeat rBPL3 gene including a repeating structure of the rBPL3 gene by tandemly binding the rBPL3 genes through spacers; preparing a recombinant plasmid by inserting the tandem repeat rBPL3 gene into an expression vector; and transforming an expression host by the recombinant plasmid. According to the method, the expression efficiency of the recombinant lectin is maximized and the activity of the manufactured recombinant lectin is enhanced.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of copending application Ser. No.15/965,993 filed on Apr. 30, 2018; which claims the benefit of KoreanPatent Application No. 10-2017-0182346 filed on Dec. 28, 2017, theentire contents of each of the above-identified applications are herebyincorporated by reference.

BACKGROUND (a) Technical Field

The present invention relates to a technique of manufacturing arecombinant protein and more particularly, to a technique ofmanufacturing a recombinant lectin protein capable of maximizingexpression efficiency and activity.

(b) Background Art

A lectin, a sugar-binding protein, has a high potential value forscientific uses such as a medical field due to a binding property withcarbohydrate, but it has been reported that the production ofrecombinant lectins having activity is limited to some lectins. Thereason is that the production efficiency of the recombinant lectin islow, and the expression of the lectin is not substantially performed bya recombination process or the activity is lost in many cases.

Meanwhile, a Bryopsis plumosa lectin (BPL3) derived from Bryopsisplumosa is a lectin having specificity to GlcNAc and GalNAc and has beenproposed to be usable as a material for a molecular probe and the like.

However, the production of a recombinant BPL3 protein using the BPL3 asa motif is not yet smoothly performed, and it is determined that thereason is that there is almost no effectiveness in the production due tothe low expression efficiency as described above.

SUMMARY OF THE DISCLOSURE

In consideration of the realities and problems of the lectin productionfield described above, an object of the present invention is to providea method of manufacturing a recombinant lectin protein capable ofsignificantly improving the expression efficiency and activity of arecombinant lectin, and particularly, to provide a method capable ofenhancing expression efficiency of a recombinant BPL3 derived fromBryopsis plumosa.

Another object of the present invention is to provide a recombinant BPL3protein manufactured by the aforementioned method.

An exemplary embodiment of the present invention provides a method ofmanufacturing a recombinant lectin protein comprising: synthesizing unitlectin genes encoding a lectin protein derived from a natural substance;preparing a tandem repeat lectin gene including a repeating structure ofthe unit lectin genes by binding the unit lectin genes tandemly throughspacers; preparing a recombinant plasmid by inserting the tandem repeatlectin gene into an expression vector; and transforming an expressionhost by the recombinant plasmid.

Another exemplary embodiment of the present invention provides a methodof manufacturing a recombinant BPL3 protein comprising: synthesizing arecombinant BPL3 (rBPL3) gene encoding a Bryopsis plumosa lectin (BPL3)protein; preparing a tandem repeat rBPL3 gene including a repeatingstructure of the rBPL3 gene by tandemly binding the rBPL3 genes throughspacers; preparing a recombinant plasmid by inserting the tandem repeatrBPL3 gene into an expression vector; and transforming an expressionhost by the recombinant plasmid.

The recombinant BPL3 gene may have base sequences represented by SEQ IDNO: 1, the expression vector may be a pET28a (+) vector, and theexpression host may be BL21 (λDE3).

The tandem repeat rBPL3 gene may include 2 to 10 rBPL3 genes.

Yet another exemplary embodiment of the present invention provides arecombinant BPL3 protein manufactured by the aforementioned method andhaving β-GlcNAc-Sp and a glycan binding specificity.

According to the manufacturing method of the recombinant lectin proteinof the present invention, it is possible to improve the recombinationefficiency of lectin derived from natural substances and manufacture arecombinant lectin protein having high activity.

Further, it is possible to remarkably improve the expression efficiencyof the recombinant BPL3 protein to the BPL3 protein derived fromBryopsis plumosa, and further, it is possible to manufacture arecombinant lectin having β-GlcNAc-Sp without reacting with natural BPL3and a glycan binding specificity.

A recombinant technology of the present invention is applied torecombinant processes of various lectins later, thereby contributinggreatly to mass production of lectins.

Meanwhile, since the glycan binding specificity of the lectin obtainedmay be minutely changed according to the repetition degree of the genecodon having a tandem repeat structure, it will be expected to morediversify and specialize the utilization of the lectin later.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present invention, and wherein:

FIG. 1 is a schematic diagram for comparing a single structure and arepeating structure of a recombinant lectin gene;

FIG. 2 is a comparison diagram of a Bryopsis plumosa-derived BPL3 genehaving SEQ ID NO: 2, an optimized recombinant BPL3 gene sequence havingSEQ ID NO: 1, and a recombinant BPL3 protein having SEQ ID NO: 3;

FIG. 3 is a diagram illustrating results of evaluating expressioncharacteristics of a lectin (rD2BPL3) expressed by the repeatingstructure and a lectin (rD1BPL3) expressed by the single structure;

FIG. 4 is a graph for comparing expression rates of the rD2BPL3 for eachIPTG concentration and for each time;

FIG. 5 is a diagram for confirming a purification result of rBPL3through Ni-NTA affinity chromatography;

FIG. 6 is a diagram illustrating an activity change and a SDS-PAGEresult according to a urea concentration;

FIG. 7 is a photograph for confirming hemagglutination activity ofrefolded rBPL3 in types A and B;

FIG. 8 is a photograph showing that the activity of the refolded rBPL3is inhibited by N-acetyl D-glucosamine and N-acetyl D-glactosamine; and

FIG. 9 is a graph for comparing glycan binding specificities of NativeBPL3, rD1BPL3, and rD2BPL3.

DETAILED DESCRIPTION

Hereinafter, a method of manufacturing a recombinant lectin protein ofthe present invention will be described in detail. However, thefollowing descriptions are illustrative for helping the understanding ofthe present invention, and the technical spirit of the present inventionis not limited to the following descriptions. The technical spirit ofthe present invention may be interpreted or limited only by appendedclaims to be described below.

In order to manufacture a recombinant lectin protein of the presentinvention, first, unit lectin genes encoding a lectin protein derivedfrom a natural substance to be recombined needs to be synthesized.

A gene sequence of the lectin derived from the natural substance may beeasily obtained by a known DB or the like. Using the obtained sequence,base sequences are designed and synthesized according to an expressionhost to be applied. The ‘unit lectin gene’ refers to an optimized genecodon synthesized above. The unit lectin gene may be synthesized bycopying a sequence structure of a natural lectin having a repeatedsequence. However, the remaining base sequence except for the copyingregion is modified and designed to be different from the sequence of thenatural lectin in order to maximize the applied host and the expressionefficiency.

The prepared unit lectin genes are not used as they are, but aresubjected to repetitive structuring processes. That is, the unit lectingenes are tandemly bound to each other through spacers to prepare atandem repeat lectin gene including the repeating structure of the unitlectin genes. The spacer is a short base sequence that tandemly bindsthe unit lectin genes, and the binding between the repeated genes may bevariously performed by employing a known gene manipulation technique.

The tandem repeat lectin gene includes at least two repeat regions, thatis, two or more unit lectin genes, and the repetition degree or therepetition number may be determined in consideration of variousvariables, such as application fields of the recombinant lectin and agene sequence of the lectin derived from the natural substance. However,if the repetition number is too large, compatibility with an expressionvector may be deteriorated, and thus, repeating of 10 times or more isnot preferable.

Next, a recombinant plasmid is prepared by inserting the tandem repeatlectin gene into an expression vector. Since a type of expression vectoris a variable that can affect the expression efficiency of the lectin,the expression vector needs to be carefully selected by consideringvarious factors such as the application fields of the lectin andcharacteristics of the lectin derived from the natural substance asdescribed above in addition to the type of expression host.

Finally, the recombinant lectin protein may be expressed through atransformation process by applying the recombinant plasmid to theexpression host. As the expression host, bacteria and the like are used,and a type of expression host has an organic relation with the designand the synthesis process of the unit lectin genes.

Compared with the production method using only the unit lectin genes, inthe case of using the gene subjected to the repetitive structuringprocess, the expression efficiency is remarkably exhibited and theexpression efficiency is increased exponentially. In addition, thelectin prepared using the repeating structural gene may exhibit a minutecharacteristic change as compared with the lectin derived from thenatural substance, and thus various studies for systematizing thecausality between the repeating structure and the lectin characteristicwill be promoted later.

Hereinafter, as an exemplary embodiment of the present invention, amethod of manufacturing a recombinant lectin (rBPL3) protein usingBryopsis plumosa lectin (BPL3) derived from Bryopsis plumosa as a motifwill be described in detail through detailed Examples, experiments, andthe like. Meanwhile, the technical spirit of the present invention isnot restricted or limited from the following detailed descriptions. Inaddition, the following descriptions may be made with reference to theaccompanying drawings.

Example

Preparation of Vector for Producing Recombinant Protein

A gene sequence of Bryopsis plumosa lectin 3 (BPL3) was obtained fromNCBI DB (ACC. KX867966). The gene sequence was optimized with genecodons of the bacteria using a Geneious program. The BPL3 gene wassynthesized by copying a sequence structure of lectin having a repeatedsequence. The BPL3 gene was cloned into an expression vector pET28a (+)and transformed into an expression host BL21 (λDE3). Transformants wereselected from an LB medium containing 25 μg/mL of kanamycin.

FIG. 1 is a schematic diagram for comparing a single structure and arepeating structure of a recombinant lectin gene. Referring to FIG. 1, arecombinant lectin (rD2BPL3) gene having a repeating structure wasprepared by binding unit recombinant lectin (rD1 BPL3) genes by spacers,and restrictive enzyme sites were inserted into the ends of the singlestructure and the repeating structure to discriminate each structure.

FIG. 2 is a comparison diagram of a Bryopsis plumosa-derived BPL3 geneand an optimized recombinant BPL3 gene sequence. Referring to FIG. 2,the optimized recombinant BPL3 gene includes a region that repeatedlyoverlaps with a BPL3 gene derived from the Bryopsis plumosa, and basesequences of some spaced sections were modified and designed. On theother hand, base sequences of the optimized recombinant BPL3 gene wasrepresented by SEQ ID NO: 1.

Optimization of Expression of Recombinant Protein

Optimal conditions for expression of recombinant proteins weredetermined by measuring expression rates according to expressiontemperatures (20, 25, 30, and 37° C.), culture times (1, 3, 5, and 7hours) and IPTG concentrations (0.1, 0.2, 0.5 and 1 mM), respectively.Protein expression was induced by adding IPTG at a concentration ofbacteria of OD 0.4 to 0.6. The total protein for measuring the proteinexpression rate was added with a 1×SDS sample buffer to be 0.2 mL/mLculture and then heated at 90° C. for 5 minutes to be obtained. Proteinextracts were centrifuged at 20,000 g for 5 minutes to remove insolubleresidues and subjected to SDS-PAGE.

Overexpression and Purification of Recombinant BPL3

A bacterial culture solution (500 mL) was centrifuged at 5,000 g for 10minutes, and the precipitate was dissolved using 50 mL of Ureaextraction buffer (50 mM NaH2PO4, 300 mM NaCl, 8 M Urea, pH 8.0).Bacteria were ruptured using a sonicator (22% amplitude, 5 sec/3 sec(On/Off), 20 minutes) and centrifuged to obtain a supernatant. The rBPL3was purified from bacterial fractions using an NGC chromatography system(BIO-RAD) and 1 mL Ni-NTA affinity chromatography. The bound rBPL3 waseluted sequentially using 75 mM, 125 mM, and 250 mM of imidazoles. Thepurify of the eluted fractions was confirmed using SDS-PAGE, and thefractions containing the rBPL3 was collected by one tube.

[Experiment and Evaluation]

Hereinafter, for convenience, the recombinant lectin obtained by thegene having the single structure is referred to as ‘rD1BPL3’, and therecombinant lectin obtained by the gene having the repeating structureis referred to as ‘rD2BPL3’. In addition, BPL3 derived from Bryopsisplumosa is referred to as Native BPL3 as a comparative target.

Evaluation of Expression Rate

FIG. 3 is a diagram illustrating results of evaluating expressioncharacteristics of a lectin (rD2BPL3) expressed by the repeatingstructure and a lectin (rD1BPL3) expressed by the single structure.

After induction by IPTG, a difference in expression rate between therepeating structure (rD2BPL3) and the single structure (rD1BPL3) wasconfirmed. BPL3s having the single structure and the repeating structureall were successfully expressed in bacteria. The rD2BPL3 had 10 timeshigher expression rate than the rD1 BPL3.

Referring to FIG. 3, as a result of an optimizing experiment forproducing rBPL3 in transformed E. coli BL21 (DE3), the expression rateof the rBPL3 was high at the rD2BPL3 as compared with the rD1BPL3.

In FIG. 3, details of (A), (B) and (C) are as follows.

A: rD1BPL3 SDS-PAGE result. M; marker, Lane 1; uninduced protein, Lane2; induced protein

B: rD2BPL3 SDS-PAGE result. M; marker, Lane 1; uninduced protein, Lane2; induced protein (0.4 mM IPTG)

C: result of comparing expression amounts of rD1 BPL3 and rD2BPL3

Evaluation of Expression Rate for Each IPTG Concentration

FIG. 4 is a graph of comparing expression rates of rD2BPL3 for each IPTGconcentration and for each time. Referring to FIG. 3, in order todetermine optimal expression conditions of the rD2BPL3, an expressionrate for each IPTG concentration and an expression rate according to thetime were compared. The highest expression rate was shown at 1 mM ofIPTG concentration, and the culture time did not affect the proteinexpression.

In FIG. 4, details of (A) and (B) are as follows.

A: Expression rate according to IPTG concentration. M; marker, Lane 1;uninduced protein, Lane 2-5; induced protein (IPTG 0.1 mM, 0.2 mM, 0.5mM, 1 mM)

B: rD2BPL3 expression rate according to time and temperature (0.4 mMIPTG; 1, 3, 5, 7(h))

Ni-NTA Affinity Chromatography

FIG. 5 is a diagram of confirming a purification result of rBPL3 throughNi-NTA affinity chromatography.

Referring to FIG. 5, BPL3 was purified purely from a bacterial culturesolution using Ni-NTA affinity chromatography. Most of the rD2BPL3 wasisolated from a column at 75 mM of imidazole.

In FIG. 5, details of (A), (B) and (C) are as follows.

A: Chromatographic purification

B: M; maker, Lane 1; crude protein, Lane 2; flow-through, Lane 3;elution (75 mM Imidazole)

C: Purified recombinant lectins; M, Molecular weight marker; lane 1;rD1BPL3, lane 2; rD2BPL3

Establishment of Refolding Conditions

FIG. 6 is a diagram illustrating an activity change and a SDS-PAGEresult according to a urea concentration. Referring to FIG. 6,denaturated rD2BPL3 was refolded using a instantaneous dilution method.When the protein was diluted to 2M Urea or less, most of the protein wasinsolubilized and the recovery rate was less than 10%. The proteinrecovery rate was about 50% under about 2M Urea. As the result ofmeasuring a change in activity according to a concentration, the highestactivity was shown at the 2M Urea.

Evaluation of Hemagglutination Activity and Sugar-Binding Property ofrD2BPL3

The hemagglutination activity of rD2BPL3 was measured. The purifiedrD2BPL3 coagulated blood cells of types A and B and strongly reactedwith the A type blood cell. FIG. 7 is a photograph for confirminghemagglutination activity of refolded rBPL3 in types A and B. Thisresult is the same result as the hemagglutination characteristic ofexisting Native BPL3.

FIG. 8 is a photograph showing that the activity of the refolded rBPL3is inhibited by N-acetyl D-glucosamine and N-acetyl D-glactosamine.Referring to FIG. 8, experiments on inhibition of hemagglutinationactivity for 10 kinds of sugars including GlcNAc and GalNAc whichinhibited hemagglutination activity of Native BPL3 were conducted. Thehemagglutination activity of rBPL3 was inhibited by GlcNAc (125 mM) andGalNAc (62.5 mM) the same as the native BPL3 identified in Han et al.,2010.

Table 1 below shows results of confirming that the Native BPL3 and therD2BPL3 inhibit the hemagglutination activity by the same sugar.

TABLE 1 Minimum inhibitory concentration Substance Native BPL3 rD2BPL3Fetuin 19.53^(§)  4.88^(§) d-Mannose NI NI l-Fucose NI NI d-Fructose NINI β-Lactose NI NI N-acetyl-d-glucosamine 125   62.5 N-acetyl-d-galactosamine 62.5  31.25 d-Galactose NI NI d-Glucose NI NId-Maltose NI NI ^(§)concentration, μg/mL, NI, the absence of inhibitionat 500 mM.

Measurement of Glycan Binding Specificity

Affinity with glycans was measured using RayBio® Glycan Array 100. TherBPL3 and the Native BPL3 were conjugated with biotin and then dialyzedto remove unreacted biotin.

FIG. 9 is a graph for comparing glycan binding specificities of NativeBPL3, rD1BPL3, and rD2BPL3. Referring to FIG. 9, the Native BPL3 reactedwith 5 glycans of 100 glycans and observed a strong signal for a glycanof Gal-β-1,3-GalNAc-α-Sp. The rD2BPL3 reacted with 8 glycans of 100glycans and observed a strong signal for a glycan of β-GlcNAc-Sp. TherD1BPL3 did not observe a strong signal in 100 glycans.

The glycan array result showed that the Native BPL3 and the rD2BPL3 werespecifically bound to different sugars except for α-Man-Sp andGal-α-1,3-Gal-β-1,3-GlcNAc-β-Sp. In a coagulation inhibition experiment,both the Native BPL3 and the rD2BPL3 were not inhibited by α-Man, but asthe glycan array result, both proteins were specifically bound toα-Man-Sp. In the coagulation inhibition experiment, there is apossibility that the coagulation is not inhibited by α-Man because acompetitive reaction with more complex glycans using the blood cellsoccurs. α-Man-specific sugar-binding proteins are recognized as viralinhibitors and additional studies are required.

There is a difference in that the rD2BPL3 specifically binds toβ-GlcNAc-Sp and the Native BPL3 does not react with β-GlcNAc-Sp. On theother hand, the Native BPL3 showed a stronger binding force toGal-β-1,3-GalNAc-α-Sp. In addition, Gal-α-1,3-Gal-β-1,3-GlcNAc-β-Spshowed affinity with the two proteins. Therefore, it is determined thatthe Native BPL3 has higher affinity with the α-structure and the rBPL3has higher affinity with the β-structure.

A Gal/GalNAc binding protein has been proposed as a candidate substancefor amoebidase vaccine, and β-D-GlcNAc-D-GalNAc having the specificityof the rD2BPL3 has been proposed as a cancer biomarker and conduction ofsubsequent studies is required.

What is claimed is:
 1. A recombinant BPL3 protein comprising β-GlcNAc-Spand a glycan binding specificity, wherein the recombinant BPL3 proteinis produced by: synthesizing a recombinant Bryopsis plumosa lectin(rBPL3) gene encoding a Bryopsis plumosa lectin (BPL3) protein;preparing a tandem repeat rBPL3 gene including a repeating structure ofthe rBPL3 gene by tandemly binding the rBPL3 genes through spacers;preparing a recombinant plasmid by inserting the tandem repeat rBPL3gene into an expression vector; and transforming an expression host withthe recombinant plasmid.